This invention relates to a process for forming a pattern.
The interior side of the face plate of a color picture tube is coated with three different kinds of phosphors in dots or in stripes. This phosphor coat layer is formed in the following way. First, a mixed coating material composed of a phosphor for the first color and a photosensitive resin is applied to the interior side of the face plate and dried to form a coating film. Then, this film layer is irradiated with ultraviolet rays through the holes of a shadow mask. The ultraviolet rays are irradiated to the position where the electron beams for effecting emission of light from the phosphor hit, that is, the place where said phosphor is to be attached. The photosensitive resin at the irradiated portions is insolubilized, resulting in insolubilization of the entire layer in the portions. Then the layer is washed with a solvent, retaining the insolubilized portions alone on the face plate while removing the other portions of the layer by dissolution. Then the same operation as said above is performed with the layer formed from a mixture of a phosphor for the second color and a photosensitive resin, and this is followed by the same operation by using a mixture of a phosphor for the third color and a photosensitive resin.
As appreciated from the foregoing explanation, the color picture tube phosphor surface forming process is complicated, and multiple times of repetition of wet coating, water washing and drying are required, so that simplification of such a process is quite desirable.
As an improvement on such process, some of the present inventors previously proposed, in Japanese Patent Application Kokai (Laid-Open) No. 126861/78, a method of forming a color picture tube phosphor surface in a considerably simpler manner than the prior art. This method was attained on the basis of a new finding that the photolytic product of an aromatic diazonium salt has an ability to accept powder particles, and it is characterized by (1) coating the inner surface of the face plate of a color picture tube with a photosensitive composition containing an aromatic diazonium salt as a photosensitive component and getting sticky upon exposure to light, thereby forming a thin coating layer on said surface, (2) subjecting said thin layer to patternwise exposure to make the exposed portions sticky, and (3) contacting powder particles with the exposed thin layer to have said powder particles accepted by said thin layer.
According to this method, mere repetition of exposure and powder contact is required for the phosphors of the second and third colors, and when the coating film is once formed, it is possible to form as many phosphor patterns as desired. This method, however, has a drawback in that the processing time is rather long due to a somewhat lower sensitivity of the photosensitive component than conventional photosensitive resins.